I just got the Cybook Gen3 earlier this week, but did not get a cover with it. I was able to create my own cover out of an old gutted
Moleskine notebook and some velcro tape. The only other thing I needed was a swiss army knife to remove the insides of the notebook. The final result is a pretty good looking cover that is non-leather (the cover material is oilcloth covered cardboard). I may still add a small amount of padding on left hand flap, but I need to find the right material first.